Method of hemodilution facilitated by monitoring oxygenation status

Abstract

A method for hemodiluting a patient is disclosed which includes the steps of administering a biocompatible oxygen carrier in conjunction with surgery or organ ischemia or infarct while assessing the patient's PvO2 or other oxygenation indices, and administering to the patient additional oxygen carrier or autologous blood in response to the PvO2 value if necessary to maintain the PvO2 at or above the desired level.

Description

FIELD OF THE INVENTIONThe present invention relates to improved medical procedures involving hemodilution. The improved method includes the administration of an oxygen carrier, the continuous monitoring of the mixed venous partial pressure of oxygen (PvO.sub.2) or other tissue oxygenation indices, and the administration of autologous blood or additional oxygen carrier to maintain the PvO.sub.2 or other indices at or above a predetermined level.BACKGROUND OF THE INVENTIONMore than 13 million units of blood are collected each year in the United States alone, and about 10 million of these units are transfused into 4 million recipients. Of the transfused units, about two-thirds are used during surgical procedures, and the remainder are used primarily for treating severe anemia or in emergency indications. Experience from clinical studies suggests that postoperative recovery can be shortened if hemoglobin concentrations are not allowed to fall to below 10 g / dL, the previously generally a...

AI Technical Summary

Benefits of technology

The present invention also includes a method for the treatment of organ ischemia or infarct, including myocardial infarction, comprising the steps of removing a portion of the blood of a patient in need of treatment for organ ischemia or infarct and intravenously administering a biocompatible liquid in sufficient quantity to reduce the patient's blood hemoglobin level to a desired concentration; and intravenously administering a biocompatible non-red cell oxygen carrier in conjunction with the removing step to maintain oxygenation of the patient's tissues at or above a predetermined level. In one embodiment, the biocompatible liquid comprises a hemodiluent. In another embodiment, the hemodiluent is administered separately from the oxygen carrier. The oxygen carrier and biocompatible liquid may be the same or different, and may be as described above. The method advantageously also includes the step of administering oxygen breathing gas to the patient during the method. The amount of oxygen carrier administered is preferably between about 0.5 and 10 ml / kg, based on the body weight of the patient. As above, one preferred concentration of hemoglobin after hemodilution is about 8 g / dL. In order to assure adequate oxygenation of tissue including myocardium, the method further comprises the step of assessing the patient's tissue oxygenation by assessing PvO.sub.2, as discussed above, to maintain a desired value of PvO.sub.2 at a value, for example, of about 40 mmHg. In one modification of the method, the oxygen carrier constitutes at least a part of the biocompatible liquid.

Problems solved by technology

Despite an increased awareness and acceptance of the benefits of autologous blood transfusion, recent studies have revealed the widespread underutilization of autologous predonation (which is estimated to represent only 2-5% of all units drawn nationwide).

The use of such blood substitutes in large volumes to replace blood used in transfusions has not been entirely satisfactory in earlier applications.

For example, early studies using FLUOSOL as a large volume blood substitute found that following blood loss, FLUOSOL was "unnecessary in moderate anemia and ineffective in sever anemia."

Thus, it was concluded that use of fluorocarbon emulsions as blood substitutes would not provide a significant benefit in severely anemic and bleeding patients.

Indeed, although the U.S. Food & Drug Administration approved FLUOSOL in 1989 for use as a perfusion agent to enhance myocardial oxygenation during percutaneous transluminal coronary angioplasty (PTCA), it did not approve an earlier application for use as a large volume blood substitute for general use.

The problem in using fluorocarbon emulsions and hemoglobin compositions as red cell substituted or blood substitutes to compensate for blood loss from surgery, disease, or trauma lies in the relatively short circulating blood half life of those materials in vivo.

Thus, even if sufficient quantities of a red cell substitute are administered during and / or after surgery, for example, to provide adequate oxygen delivery, the oxygen carrying capacity will drop significantly long before the body can compensate by making new red cells.

Under no circumstance during current treatment methods is blood purposefully diluted, as this would dilute the concentration of red blood cells and thus impair the delivery of oxygen to the hearts.

Many cellular elements of blood, however, are detrimental in the case of myocardial infarction.

Hemodilution is not done, however, because it is also necessary to maintain high red blood-cell levels to deliver oxygen to the myocardium.

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